Yield behavior beneath hardness indentations in ductile metals, measured by three-dimensional computed X-ray tomography and digital volume correlation

In-situ X-ray computed tomography characterisation of 3D fracture evolution and image-based numerical homogenisation of concrete

“…the most precise dataset); the details of this method are described in (Mostafavi et al, 2015). The measured rotations of the sample in all loadings were found to be of the order of 0.5°.…”

“…However, in-situ XCT studies, which scan the internal structures of materials under progressive loadings so that the structural damage and fracture evolution can be examined and related to the loading process are now feasible. For example, De Kock et al (2015) have observed the fracture process in rocks under ambient freeze−thaw cycling and Nagira et al (2011) studied semi-solid carbon steels., whilst in recent years some of the authors of this paper have conducted in-situ XCT experiments to examine deformation in metal-metal composites (Baimpas et al, 2014), fatigue cracking in magnesium alloy , indentation cracking in alumina (Vertyagina et al, 2014) and ceramic composites ), tensile deformation in nuclear graphite (Marrow et al, 2016), and polymeric foams (McDonald et al 2011), liquid flow and deformation in semi-solid aluminium alloys (Cai et al, 2016), indentation deformation in a metal-matrix composite 3 (Mostafavi et al, 2015), and fracture of propagation in nuclear graphite (Mostafavi et al, 2013). For such studies to be successful, it is important to consider the experimental constraints of increasing X-ray absorption with sample dimension and density, which limits the maximum dimensions and increases the time to record tomographs, and also for digital volume correlation analysis of deformation, it is necessary that the microstructure contains sufficient "speckle" contrast that can be discerned at the experiment's resolution .…”

Digital Volume Correlation: Review of Progress and Challenges

“…Among them, the virtual fields method was used to calibrate elastic parameters for cornea [73], trabecular bone [79] and 3D particulate composite [184]. Finite element model updating was used to calibrate plastic parameters when Al-SiC composite and cast magnesium alloy were indented in-situ [162]. Such parameters were also calibrated for nodular graphite cast iron when cyclically loaded in uniaxial tension [93].…”

Observation and simulation of indentation damage in a SiC–SiCfibre ceramic matrix composite

“…Finally, the remaining minor (i.e. sub-voxel) rigid body translations and rotations were corrected [15] such that the relative displacements remote from the indentation, i.e. close to the bottom surface of the sample, were zero.…”

“…This can be done in appropriate microstructures using X-ray computed tomography (XCT) in combination with threedimensional digital image correlation (digital volume correlation or DVC) [7,8] to measure the displacements within materials [9,10,11]; sufficient contrast may be achieved by X-ray attenuation or scattering from microstructural heterogeneities of the order of the voxel 2 size. The precision of displacement resolution increases with the multi-voxel interrogation subset size, enabling DVC to measure sub-voxel displacements [12]; recently this method has been used to characterise, for instance, the fracture behaviour of polygranular quasibrittle materials [13,8], indentation cracking in brittle polycrystalline ceramics [14] and the plastic zones beneath hardness indentations in engineering alloys [15].…”